/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.stdlib.statistics.function;

import axil.stdlib.numbers.type.Int;
import axil.stdlib.numbers.type.Num;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;


/**
 * Compute the standard deviation across a collection of values.
 */
public class StdDev extends Variance {
    /**
     * Execute the specific statistical function against the given arguments.
     */
    protected Num calculate(ArrayList<Num> values) {
        final int size = values.size();
        if (size == 0) {
            return Int.zero;
        }
        /*
         * Standard Deviation = Square Root of the Variance
         */
        Num variance = super.calculate(values);
        BigDecimal var = new BigDecimal(variance.toString());
        double stdDevD = Math.sqrt(var.doubleValue());
        // Convert to a BigD to adjust the scale back to the scale of the variance.
        BigDecimal stdDev = new BigDecimal(stdDevD);
        stdDev = stdDev.setScale(var.scale(), RoundingMode.HALF_EVEN);
        return Num.convert(stdDev);
	}
}
